Field of the Invention
The present invention relates to a new and useful apparatus for the delivery of foam to textile fabrics and more particularly relates to a device for applying foam under pressure to a moving fabirc in an even manner so that consistent, high-quality foam finished or dyed fabrics are obtained.
In recent years and in particular since the advent of higher energy costs, much research effort has been devoted to the development of fabric finishing and dyeing apparatus which are more energy efficient than conventional finishing and dyeing devices. Conventional devices for finishing a fabric include a holding tank which contains a bath of finishing agent. A moving fabric is immersed in the bath and thereafter dried and further processed. The immersion of the fabric causes absorption of the finishing agent (dyestuff or sizing agent or the like) by the fibers of the moving fabric. This may result in the swelling and distortion of the fabric and the consequent weakening of the fibers. The conventional devices also have the substantial cost disadvantage of requiring substantial energy to remove the solution or dispersion liquid in which the finishing agent or dyestuff is contained.
Foam finishing apparatus, such as that described in U.S. Pat. No. 4,023,526, are used as alternatives to the conventional, immersion type fabric finishing devices. The advantage is that substantially less liquid per unit amount of finishing agent need be applied to and then removed from the fabric.
A device which is commonly used today and suitable for many foaming processes is referred to in the industry as a single knife applicator. This device includes basically a foam dam suspended above a moving fabric and a doctor blade mounted to the foam dam on the side thereof which is downstream with respect to the direction of fabric movement. A foam finish is contained within the foam dam which is in contact with a surface of the moving fabric. Foam is applied to the moving fabric and excess foam is scraped from the fabric by the doctor blade. The doctor blade causes a "foam bank" to build within the foam dam.
There are many inherent disadvantages in using the single knife applicator described above for applying foams to a moving fabric. One disadvantage is that it is difficult to closely control the exact amount of foam which is applied to the fabric. The foam bank is constantly changing in size and it is difficult to achieve a steady state operation. The operator of the device must control the height of the foam bank which is applied and maintained, the density of the foam (or its inverse, known as the blow ratio), the amount of liquid containing the foaming agent which is supplied to the applicator per unit time and the stability of the foam which is created, the latter being essentially a function of the choice and amount of surfactant which is used. The rate of absorption of the foam onto the moving fabric is determined by the wetting action of the foam as it contacts the moving fabric.
The problems associated with the single knife applicator have been essentially eliminated by the foam finishing apparatus disclosed in applicant's copending application Ser. No. 06/416,853, filed Sept. 13, 1982, which is herein incorporated by reference. The apparatus described in the above application includes a pressure manifold for applying foam under pressure to a moving fabric in contact therewith. The pressure manifold includes at least two conduits, an inner conduit to which foam is supplied under pressure having formed therein an effluent port extending over at least a portion of its length and an outer conduit, larger than the inner conduit and surrounding the inner conduit, the outer conduit having a slotted port formed along its length for delivery of foam under pressure to the moving fabric.
The present application discloses an alternative structure for a pressure manifold for a foam applicator to that which is described in the copending application Ser. No. 06/416,853. The invention is particularly useful in applying a foaming agent to wide fabrics where constant and uniform distribution of foam over the entire width of the fabric is required.